Method of making a biosensor

ABSTRACT

A method of making a biosensor is provided. The biosensor includes an electrically conductive material on a base and electrode patterns formed on the base, the patterns having different feature sizes. The conductive material is partially removed from the base using broad field laser ablation so that less than 90% of the conductive material remains on the base and that the electrode pattern has an edge extending between two points. A standard deviation of the edge from a line extending between two points is less than about 6 μm

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a Divisional of U.S. application Ser. No.10/601,144 filed Jun. 20, 2003, which is a Continuation-in-Part of U.S.Pat. No. 6,662,439, issued Dec. 16, 2003; a Continuation-in-Part of U.S.Pat. No. 6,645,359, issued Nov. 11, 2003; a Continuation in Part of U.S.Pat. No. 6,767,440 B1, issued Jul. 27, 2004; and a Continuation in Partof U.S. application Ser. No. 10/264,891, filed Oct. 4, 2002, each ofwhich are hereby incorporated by reference in its entirety.

TECHNICAL FIELD

The present invention relates to a method of making a biosensor, morespecifically a biosensor having electrode sets formed by laser ablation.

BACKGROUND AND SUMMARY OF THE INVENTION

Electrochemical biosensors are well known and have been used todetermine the concentration of various analytes from biological samples,particularly from blood. Examples of such electrochemical biosensors aredescribed in U.S. Pat. Nos. 5,413,690; 5,762,770 and 5,798,03 1; and6,129,823 each of which is hereby incorporated by reference.

It is desirable for electrochemical biosensors to be able to analyzeanalytes using as small a sample as possible, and therefore it isnecessary to minimize the size its parts, including the electrodes, asmuch as possible. As discussed below, screen-printing, laser scribing,and photolithography techniques have been used to form miniaturizedelectrodes.

Electrodes formed by screen-printing techniques are formed fromcompositions that are both electrically conductive and which arescreen-printable. Furthermore, screen printing is a wet chemicaltechnique that generally allows for the reliable formation of structuresand patterns having a gap width or feature size of approximately 75 μmor greater. Such techniques are well known to those of ordinary skill inthe art.

Laser scribing is a technique that usually uses a high power excimerlaser, such as a krypton-fluoride excimer laser with an illuminationwavelength of 248 nm, to etch or scribe individual lines in theconductive surface material and to provide insulating gaps betweenresidual conductive material which forms electrodes and other desiredcomponents. This scribing is accomplished by moving the laser beamacross the surface to be ablated. The scribing beam generally has arelatively small, focused size and shape, which is smaller than thefeatures desired for the product, and the formation of the producttherefore requires rastering techniques. It is therefore appreciatedthat such a technique can be rather time consuming if a complexelectrode pattern is to be formed on the surface. Still further, it isappreciated that the precision of the resulting edge is rather limited.This scribing technique has been used to ablate metals, polymers, andbiological material. Such systems are well known to those of ordinaryskill in the art, and are described in U.S. Pat. Nos. 5,287,451,6,004,441, 6,258,229, 6,309,526, WO 00/73785, WO 00/73788, WO 01/36953,WO 01/75438, and EP 1 152 239 each of which is hereby incorporated byreference. It would be desirable to have a new method of formingelectrodes which allows precise electrode edges, a variety of featuresizes, and which can be formed in a high speed/throughput fashionwithout the use of rastering.

According to the present invention a method of making a biosensorelectrode pattern is provided. The method comprises the steps ofproviding an electrically conductive material on a base and formingelectrode patterns on the base using broad field laser ablation. In oneaspect at least two electrode patterns are formed on the base that havedifferent feature sizes.

According to the present invention a method of making a biosensor isprovided. The method comprises the steps of providing an electricallyconductive material on a base and partially removing the conductivematerial from the base using laser ablation so that less than 90% of theconductive material remains on the base and at least one electrodepattern is formed from the conductive material. In one aspect, at leastone electrode pattern has an edge extending between two points, astandard deviation of the edge from a line extending between two pointsbeing less than about 6 μm along the length of the edge.

According to the present invention a method of making a biosensor isprovided. The method comprises the steps of providing an electricallyconductive material on a base, forming electrode patterns on the baseusing broad field laser ablation, wherein at least two electrodepatterns have different feature sizes, and extending a cover over thebase. In one aspect, the cover and base cooperate to define asample-receiving chamber and at least a portion of the electrodepatterns are positioned in the sample-receiving chamber.

According to the present invention a method of making a biosensorelectrode set is provided. The method comprises providing a laser systemhaving a lens and a mask, and ablating through a portion of a firstmetallic layer with a laser, to form an electrode pattern, the patternof ablation being controlled by the lens and the mask. In one aspect,the metallic layer is on an insulating base.

According to another aspect of the present invention, a method of makinga biosensor strip is provided. The method comprises providing a lasersystem having at least a laser source and a mask, and forming anelectrode set by ablating through a portion of a metallic layer with alaser, a pattern of ablation being controlled by the mask, wherein saidmetallic layer is on an insulating base.

Still further, according to the present invention a method of making abiosensor is provided. The method comprises providing an electricallyconductive material on a base and forming a pre-determined electrodepattern on the base using laser ablation through a mask, the mask havinga mask field with at least one opaque region and at least one windowformed to allow a laser beam to pass through the mask and to impactpredetermined areas of the electrically conductive material.

According to the present invention a method of making a biosensorelectrode set is provided. The method comprises providing a laser systemhaving a lens and a mask, ablating through a portion of a metallic layerwith a laser, to form an electrode pattern, the pattern of ablationbeing controlled by the lens and the mask, wherein said first metalliclayer is on an insulating substrate.

According to the present invention a method of making an electrode setribbon is provided. The method comprises providing a laser system havinga lens and a mask and ablating through a portion of a metallic layerwith a laser, to form a plurality of electrode patterns. The pattern ofablation is controlled by the lens and the mask, the metallic layer ison an insulating substrate, and the electrode set ribbon comprises aplurality of electrode sets.

Still further according to the present invention a method of making asensor strip is provided. The method comprises providing a laser systemhaving a lens and a mask, forming an electrode set by ablating through aportion of a first metallic layer with a laser, and cutting saidsubstrate, to form a strip. A pattern of ablation is controlled by thelens and the mask and the first metallic layer is on an insulatingsubstrate.

The following definitions are used throughout the specification andclaims:

As used herein, the phrase “electrically conductive material” refers toa layer made of a material that is a conductor of electricity,non-limiting examples of which include a pure metal or alloys.

As used herein, the phrase “electrically insulative material” refers toa material that is a nonconductor of electricity.

As used herein, the term “electrode” means a conductor that collects oremits electric charge and controls the movement of electrons. Anelectrode may include one or more elements attached to a commonelectrical trace and/or contact pad.

As used herein, the term “electrical component” means a constituent partof the biosensor that has electrical functionality.

As used herein, the phrase “electrode system” refers to an electricalcomponent including at least one electrode, electrical traces andcontacts that connect the element with a measuring instrument.

As used herein, the phrase “electrode set” is a grouping of at least twoelectrodes that cooperate with one another to measure the biosensorresponse.

As used herein, the term “pattern” means a design of one or moreintentionally formed gaps, a non-limiting example of which is a singlelinear gap having a constant width. Not included in the term “pattern”are natural, unintentional defects.

As used herein, the phrase “insulative pattern” means a design of one ormore intentionally formed gaps positioned within or between electricallyinsulative material(s). It is appreciated that electrically conductivematerial may form the one or more gaps.

As used herein, the phrase “conductive pattern” means a design of one ormore intentionally formed gaps positioned within or between electricallyconductive material(s). It is appreciated that exposed electricallyinsulative material may form the one or more gaps.

As used herein, the phrase “microelectrode array” means a group ofmicroelectrodes having a predominantly spherical diffusionalcharacteristic.

As used herein, the phrase “macroelectrode array” means a group ofmacroelectrodes having a predominantly radial diffusionalcharacteristic.

As used herein, the phrase “electrode pattern” means the relativeconfiguration of the intentionally formed gaps situated between theelements of electrodes in an electrode set. Non-limiting examples of“electrode patterns” include any configuration of microelectrode arraysand macroelectrode arrays that are used to measure biosensor response.

As used herein, the phrase “feature size” is the smallest dimension ofgaps or spaces found in a pattern. For example, in an insulativepattern, the feature size is the smallest dimension of electricallyconductive gaps found within or between the electrically insulativematerial(s). When, however, the pattern is a conductive pattern, thefeature size is the smallest dimension of electrically insulative gapsfound within or between the electrically conductive material(s).Therefore, in a conductive pattern the feature size represents theshortest distance between the corresponding edges of adjacent elements.

As used herein, the term “interlaced” means an electrode pattern whereinthe elements of the electrodes are interwoven relative to one another.In a particular embodiment, interlaced electrode patterns includeelectrodes having elements, which are interdigitated with one another.In the simplest form, interlaced elements include a first electrodehaving a pair of elements and a second electrode having a single elementreceived within the pair of elements of the first electrode.

As used herein, the term “ablating” means the removing of material. Theterm “ablating” is not intended to encompass and is distinguished fromloosening, weakening or partially removing the material.

As used herein, the phrase “broad field laser ablation” means theremoval of material from a substrate using a laser having a laser beamwith a dimension that is greater than the feature size of the formedpattern. Broad field ablation includes the use of a mask, pattern orother device intermediate a laser source and a substrate, which definesa pattern in which portions of the laser beam impinge on the substrateto create variable and multiple patterns on the substrate. Broad fieldlaser ablation simultaneously creates the pattern over a significantarea of the substrate. The use of broad field laser ablation avoids theneed for rastering or other similar techniques that scribe or otherwisedefine the pattern by continuous movement of a relatively focused laserbeam relative to the substrate. A non-limiting example of a process forbroad field laser ablation is described below with reference tobiosensor 210.

As used herein, the term “line” means a geometric figure formed by apoint moving in a first direction along a pre-determined linear orcurved path and in a reverse direction along the same path. In thepresent context, an electrode pattern includes various elements havingedges that are defined by lines forming the perimeters of the conductivematerial. Such lines demarcating the edges have desired shapes, and itis a feature of the present invention that the smoothness of these edgesis very high compared to the desired shape.

As used herein, the term “point” means a dimensionless geometric objecthaving no properties except location.

As used herein, the term “smooth” means an edge of a surface deviatingfrom a line extending between two points not more than about 6 82 m.Further, for patterns having a feature size of about 5 μm or less,“smooth” means an edge of a surface deviating from a line extendingbetween two points less than one half the feature size of the conductivepattern. For example, such lines demarcate the edges that have desiredshapes, and the smoothness of these edges is very high compared to thedesired shape.

As used herein, the phrase “biological fluid” includes any bodily fluidin which the analyte can be measured, for example, interstitial fluid,dermal fluid, sweat, tears, urine, amniotic fluid, spinal fluid andblood.

As used herein, the term “blood” includes whole blood and its cell-freecomponents, namely plasma and serum.

As used herein, the term “working electrode” is an electrode at whichanalyte, or product, is electrooxidized or electroreduced with orwithout the agency of a redox mediator.

As used herein, the term “counter electrode” refers to an electrode thatis paired with the working electrode and through which passes anelectrochemical current equal in magnitude and opposite in sign to thecurrent passed through the working electrode. The term “counterelectrode” is meant to include counter electrodes, which also functionas reference electrodes (i.e., a counter/reference or auxiliaryelectrode).

As used herein, the term “electrochemical biosensor” means a deviceconfigured to detect the presence and/or measure the concentration of ananalyte by way of electrochemical oxidation and reduction reactionswithin the biosensor. These reactions are transduced to an electricalsignal that can be correlated to an amount or concentration of theanalyte.

Additional features of the invention will become apparent to thoseskilled in the art upon consideration of the following detaileddescription of the preferred embodiment exemplifying the best mode knownfor carrying out the invention. It should be understood, however, thatthe detailed description and the specific examples, while indicatingembodiments of the invention, are given by way of illustration only,since various changes and modifications within the spirit and scope ofthe invention will become apparent to those skilled in the art from thisdetailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The following drawings form part of the present specification and areincluded to further demonstrate certain aspects of the presentinvention. The invention may be better understood by reference to one ormore of these drawings in combination with the detailed description ofspecific embodiments presented herein:

FIG. 1 illustrates a perspective view of a biosensor of the presentinvention;

FIG. 2 illustrates an exploded assembly view of the biosensor of FIG. 1;

FIG. 3 illustrates an enlarged plan view of the biosensor of FIG. 1showing a macroelectrode array and a microelectrode array;

FIG. 4 illustrates a diagram of an edge deviation from a line:

FIG. 5 illustrates a diagram of a gap deviation from a pre-defined widthvalue for the gap;

FIG. 6 illustrates an enlarged section of the microelectrode array ofFIG. 3;

FIG. 7 illustrates a diagram of an edge deviation from a line;

FIG. 8 illustrates a cross-section taken along lines 8-8 of FIG. 1;

FIG. 9 illustrates a cross-section taken along lines 9-9 of FIG. 1;

FIG. 10 illustrates a graph showing a deviation from mean of anelectrode edge of the microelectrode array of FIG. 3;

FIG. 11 illustrates an exploded assembly view of a biosensor inaccordance with another embodiment of the invention;

FIG. 12 illustrates an exploded assembly view of a biosensor inaccordance with another embodiment of the invention;

FIG. 13 illustrates an exploded assembly view of a biosensor inaccordance with another embodiment of the invention;

FIG. 14 illustrates an exploded assembly view of a biosensor inaccordance with another embodiment of the invention;

FIG. 15 illustrates an exploded assembly view of a biosensor inaccordance with another embodiment of the invention;

FIG. 16 illustrates an enlarged perspective view of a biosensor inaccordance with another embodiment of the invention;

FIG. 17 illustrates a view of an ablation apparatus suitable for usewith the present invention;

FIG. 18 is a view of the laser ablation apparatus of FIG. 17 showing asecond mask;

FIG. 19 is a view of an ablation apparatus suitable for use with thepresent invention;

FIG. 20 is a schematic of an electrode set ribbon of the presentinvention;

FIG. 21 is a microscopic view of a portion of an electrical componenthaving a rough edge; and

FIG. 22 is a microscopic view of a portion of an electrical componenthaving a relatively “smooth” edge.

DETAILED DESCRIPTION OF THE INVENTION

For the purposes of promoting an understanding of the principles of theinvention, reference will now be made to the embodiments illustrated inthe drawings, and specific language will be used to describe theembodiments. It will nevertheless be understood that no limitation ofthe scope of the invention is intended. Alterations and modifications inthe illustrated devices, and further applications of the principles ofthe invention as illustrated therein, as would normally occur to oneskilled in the art to which the invention relates are contemplated, aredesired to be protected.

A biosensor in accordance with the present invention provides a surfacewith electrode patterns formed thereon, the electrode patternspreferably having a smooth edge quality. It is a particular aspect ofthe present invention that precise quality is obtained for the edges ofthe electrical components located on the biosensor. Having a smooth orhigh edge quality of the elements can contribute to greater precision,accuracy, and reproducibility of test results. Further, a smooth or highedge quality also allows for a great number of electrode arrays to beformed on a defined surface area of the biosensor. By increasing theedge quality of the elements, it is possible to increase the number ofelectrode elements and thus increase the achievable functionality in thedefined surface area. These functions may include, for example: multiplemeasurement electrode pairs for simultaneous measurement of the same ordifferent analytes, including by alternative means; electrodes used toprovide correction factors for the basic measurement electrodes;electrodes for detecting dose application or sample sufficiency;multiple electrode traces to monitor electrode functioning or to providedetection or correction of defective traces; and multiple contact padsfor coupling to the foregoing functionalities, or for providingadditional features such as identification, calibration, or otherinformation pertaining to the biosensor. Further, the selectedfunctionalities for a given biosensor can be provided in a smaller spacewhen the high edge quality allows closer placement of the electricalcomponents. It is a feature of the present invention to enable all ofthis, and more, in a manner that is relatively fast, reliable and costeffective.

Specifically, a biosensor of the present invention has electricalcomponents with edges that are smooth and are precisely located. Theprecise locating of the smooth edge is important, particularly relativeto a corresponding edge of another electrical component, and especiallywith respect to a paired element. The importance and the degree ofquality of a component's edge quality and placement will vary with thenature of the component.

For macroelectrodes, it is noted that the edge smoothness and placementare important for the quality of the electrochemical results obtained byuse of the macroelectrodes. One factor in the accuracy of such a test isthe reproducibility of the area of each macroelectrode. The provision ofprecise edge smoothness and placement will yield an area that is highlyaccurate. Another factor in the use of macroelectrodes is the placementof one of the electrodes relative to the other, e.g., the position ofthe counter element(s) in relationship to the position of the workingelement(s). Moreover, since biosensors are generally operated based oncalibration methods that rely on the reproducibility of the sizes andlocations of the measuring electrodes, the ability to consistentlyproduce lots of such tests trips can enhance the results achieved withthe tests.

Similarly, the edge smoothness and placement contribute to the resultsobtained from microelectrodes. For microelectrodes, the issues can bemagnified because of the number and relatively close placement of thenumerous microelements. Poor edge quality can greatly change theoperating characteristics of microelectrodes, and the present inventionhelps to overcome this potential problem. Moreover, an advantage ofplacing microelements in close proximity is the rapid establishment ofsteady-state operation. The provision of high edge quality and preciseedge placement enables closer placement of the elements, and thereforefaster achievement of steady-state operation. In addition, such closerplacement allows for a greater number of microelements to be placed in agiven space.

The foregoing discussion also applies to various other electricalcomponents on the biosensor. Other types of electrodes may be employedon a biosensor, for example to detect dose application or samplesufficiency, or to provide correction factors for hematocrit,temperature, etc. In addition to enhancing the results obtained fromsuch additional electrode systems, the present invention allows for theinclusion of such additional functionalities in a small space. Thisallows the inclusion of such features while maintaining the overallsample-receiving chamber at a small volume.

Still further, the edge smoothness and placement accuracy contribute tothe ability to place an increased number of traces in a limited space ona biosensor. Thus, the present invention allows for multiplefunctionalities on a single biosensor requiring the use of acorresponding number, or more, of electrical traces.

The contact pads are also enhanced in view of the high quality of theedge smoothness and placement. The increased number of functionalitieson a single biosensor requires a related increase in the number ofcontact pads, which must fit on an already crowded area of the typicalbiosensor. The ability to pack more contact pads and associatedelectrical components onto the biosensor can greatly increase theutility of the biosensor.

In a first aspect, the present invention provides a high quality edgefor the various electrical components on a biosensor. The quality of theedge relates to the smoothness or uniformity of the edge relative to atheoretical profile of the edge. A non-limiting example of such a“smooth” edge formed in accordance with teachings of the presentdisclosure is shown in FIG. 22.

In one respect, the smoothness relates simply to the deviation of theedge surface relative to the theoretical line defining the desired shapeof the edge. It will be appreciated that any electrical component on abiosensor has an intended location and shape that will not be exactlyduplicated by the physical embodiment. The extent to which the actualedge of the component varies from the theoretical one is a measure ofthe smoothness of the edge. As previously discussed, a smooth edge isdefined herein as an edge for which the standard deviation for thedistances by which the actual edge points vary from the theoretical edgeconfiguration do not vary by more than a given amount. This variation isreferred to herein as the “smoothness standard deviation”. In oneaspect, the smoothness standard deviation is less than about 6 μm,preferably less than about 2 μm, and more preferably less than about 1.0μm.

As relates to the various electrical components, the extent to which agiven portion of the component is “smooth” may vary. Referring inparticular to the measuring electrodes, it will be appreciated thatcertain edges of the elements are more critical than others. Forexample, certain edges of the counter and working electrodes areadjacent one another, while others are not. Also, certain edges arelocated within the sample-receiving chamber, and others are not. In afirst aspect, the present invention relates to providing smooth edgesfor all of the edges of the measuring electrodes. In another aspect, theinvention provides smooth edges particularly for the edges of themeasuring electrodes located within the sample-receiving chamber, andmore particularly for the edges of the measuring elements that areadjacent to one another. “Adjacent edges” in this context refers to thefact that an edge of a counter element is closest to, i.e., adjacent to,an edge of an element of a working electrode with which the counterelectrode is paired. Preferably, the edge of a measuring electrode thatcomprises an adjacent edge has a smoothness standard deviation of lessthan about 2 μm, more preferably less than about 1 μm.

As indicated previously, the present invention relates in one aspect toproviding macroelectrodes having a closely determined area. The desiredaccuracy of the provided area can vary based on the absolute size of themacroelectrode. As contemplated by the present invention, it is anaspect that the smoothness of the edge of a macroelectrode has astandard deviation of less than about 4 μm to about 6 μm along theentire length of that edge, more preferably less than about 2 μm, andmost preferably less than about 1 μm. Non-limiting examples of asuitable length of the edge are about 50 μm to about 1.5 mm, preferablyabout 250 μm to about 1 mm.

The spacing of macroelectrodes also can benefit from the presentinvention. For example, for macroelectrodes that are spaced apart by 250μm, the adjacent edges preferably have a smoothness represented by astandard deviation (from theoretical) of less than about 4 μm; forelements spaced apart by 100 μm, the standard deviation is preferablyless than about 2 μm. In this regard, the smoothness standard deviationfor macroelectrodes is preferably less than about 2% of the gap betweenadjacent macroelectrodes, more preferably less than about 1% of the gap.

For microelectrodes, the desired smoothness can differ. For example, formicroelements that are spaced apart by 50 μm, the adjacent edges have asmoothness represented by a standard deviation (from theoretical) ofless than about 6 μm, preferably less than about 2 μm, and mostpreferably less than about 1 μm. If the microelements are spaced apartby about 10 μm, then the smoothness standard deviation is preferablyless than about 1 μm, more preferably less than about 0.5 μm. Stillfurther, if the microelements are spaced apart by less than 1 μm, thenthe smoothness standard deviation is preferably less than one half thefeature size of the microelement pattern. In general, the smoothnessstandard deviation for microelectrodes is preferably less than about 5%of the gap between adjacent microelements or feature size, morepreferably less than about 2% of the gap or feature size.

It is also an aspect of the present invention that the other electricalcomponents can be provided with smooth edges to facilitate closeplacement of such components. Such other components preferably have asmoothness standard deviation that is less than about 6 μm, and morepreferably less than about 2 μm. For spacings less than 1 μm, then thesmoothness standard deviation is preferably less than one half the gapbetween the adjacent electrical components.

The present invention also provides for the accurate placement of theelectrical components relative to one another and to the overallbiosensor. The relative placement of components is achieved, at least inpart, by the use of broad field laser ablation that is performed througha mask or other device that has a precise pattern for the electricalcomponents. The relative placement of the components therefore does notdepend on the controlled movement of a rastering laser or of thesubstrate relative to the rastering laser. Moreover, this accuratepositioning of adjacent edges is further enhanced by the closetolerances for the smoothness of the edges.

Therefore, in a further aspect the invention provides electricalcomponents that have gaps or features that are precisely controlled.More specifically, the electrical components will have designed,theoretical configurations for the gaps between adjacent edges, whereasthe physical embodiments will have variations and irregularities. Thepresent invention provides gaps between adjacent edges that are highlyuniform. Specifically, the present invention provides a “uniform gap”,which is defined as a gap for which the “gap standard deviation” for thewidths or spacings of the actual edge points, compared to thetheoretical spacings, do not vary by more than a given amount. In oneaspect, for example, the gap standard deviation is less than about 6 μmalong the entire length of the gap. Preferably the gap standarddeviation is less than about 2 μm, more preferably less than about 1 μm.

Related to this concept, the accurate gap dimensions for adjacent edgesare also obtained by the minimal deviations of the respective edges fromthe theoretical edges. As previously described, the edge quality ispreferably represented by a smoothness standard deviation that is lessthan about 6 μm. In a related aspect then, the gap formed between twoadjacent edges has a gap uniformity in which the standard deviation ofthe gap width is less than about 6 μm, more preferably less than about 2μm. Various aspects of the invention are presented in FIGS. 1-20 and 22,which are not drawn to scale and wherein like components in the severalviews are numbered alike.

It is appreciated that the biosensor of the present invention issuitable for use in a system for assessing an analyte in a sample fluid.In addition to the biosensor, the system includes a meter (not shown)and provides methods for evaluating the sample fluid for the targetanalyte. The evaluation may range from detecting the presence of theanalyte to determining the concentration of the analyte. The analyte andthe sample fluid may be any for which the test system is appropriate.For purposes of explanation only, a preferred embodiment is described inwhich the analyte is glucose and the sample fluid is blood orinterstitial fluid. However, the present invention clearly is not solimited in scope.

Non-limiting examples of meters suitable for use with the biosensor ofthe present invention for determination of the analyte in the samplefluid are disclosed in U.S. Pat. Nos. 4,963,814; 4,999,632; 4,999,582;5,243,516; 5,352,351; 5,366,609; 5,405,511; and 5,438,271, thedisclosures of each being incorporated herein by reference. The suitablemeter (not shown) will include a connection with electrodes of thebiosensor, and circuitry to evaluate an electrochemical signalcorresponding to the concentration of the analyte. The meter may alsoinclude electrical components that determine whether the sample fluidhas been received by the biosensor and whether the amount of samplefluid is sufficient for testing. The meter typically will store anddisplay the results of the analysis, or may alternatively provide thedata to a separate device.

The biosensor of the present invention forming part of the system canprovide either a qualitative or quantitative indication for the analyte.In one embodiment, the biosensor cooperates with the meter to indicatesimply the presence of the analyte in the sample fluid. The biosensorand meter may also provide a reading of the quantity or concentration ofthe analyte in the sample fluid. In a preferred embodiment, it is afeature of the present invention that a highly accurate and precisereading of the analyte concentration is obtained.

The biosensor is useful for the determination of a wide variety ofanalytes. The biosensor, for example, is readily adapted for use withany suitable chemistry that can be used to assess the presence of theanalyte. Most preferably, the biosensor configured and used for thetesting of an analyte in a biological fluid. Commensurate modificationsto the system will be apparent to those skilled in the art. For purposesof explanation, and in a particularly preferred embodiment, the systemis described with respect to the detection of glucose in a biologicalfluid.

The biosensor is also useful with a wide variety of sample fluids, andis preferably used for the detection of analytes in a biological fluid.In addition, the biosensor is useful in connection with reference fluidsthat are used in conventional fashion to verify the integrity of thesystem for testing.

In a preferred embodiment, the biosensor is employed for the testing ofglucose. The sample fluid in this instance may specifically include, forexample, fresh capillary blood obtained from the finger tip or approvedalternate sites (e.g., forearm, palm, upper arm, calf and thigh), freshvenous blood, and control solutions supplied with or for the system. Thefluid may be acquired and delivered to the biosensor in any fashion. Forexample, a blood sample may be obtained in conventional fashion byincising the skin, such as with a lancet, and then contacting thebiosensor with fluid that appears at the skin surface. It is an aspectof the present invention that the biosensor is useful with very smallfluid samples. It is therefore a desirable feature that only a slightincising of the skin is necessary to produce the volume of fluidrequired for the test, and the pain and other concerns with such methodcan be minimized or eliminated.

FIGS. 1-10 illustrate an aspect of the invention, which is the formingof an electrochemical biosensor 210. Biosensor 210 has two electrodepatterns having different feature sizes on a common planar surface andthus permits the accurate measurement of an analyte in a fluid.

As shown in FIG. 1, biosensor 210 comprises a base 212, conductivematerial 216 positioned on the base 212, a spacer 214, and a cover 218.The cover 218 and spacer 214 cooperate with the base 212 to define asample-receiving chamber 220 (FIG. 9) having a sample inlet opening 221for the sample fluid, and a reagent 264 for producing an electrochemicalsignal in the presence of a test analyte. The biosensor 210 is formed asa test strip, particularly one having a laminar construction providingan edge or surface opening to the sample-receiving chamber 220. Thereagent 264, as shown in FIGS. 2 and 9, is exposed by thesample-receiving chamber 220 to provide the electrochemical signal to aworking electrode also positioned within the chamber 220. In appropriatecircumstances, such as for glucose detection, the reagent may contain anenzyme and optionally a mediator.

The base 212 of biosensor 210 includes edges 222 that define oppositeends 224, 226 and sides 228, 230 extending between the ends 224, 226.Base 212 also has a top surface 232 supporting the conductive material216 and an opposite bottom surface 234 (FIGS. 8 and 9). Illustratively,base 212 has a length of 40 mm and a width of 10 mm. It is appreciated,however that these values are merely illustrative and that thedimensions of the base 212 may vary in accordance with the presentdisclosure.

The base 212 is a substrate that is formed from an insulating material,so that it will not provide an electrical connection between electrodesformed from the conductive material 216. Non-limiting examples ofsuitable insulating materials include glass, ceramics and polymers.Preferably, the base is a flexible polymer and has a strong absorbancein the UV. Non-limiting examples of suitable materials includepolyethylene terephtalate (PET), polyethylene naphthalate (PEN), andpolyimide films. The suitable films are commercially available asMELINEX®, KALADEX® and KAPTON®, respectively from E.I. duPont deNemours, Wilmington, Del., USA (“duPont”) and UPILEX®, a polyimide filmfrom UBE Industries Ltd, Japan. Preferred materials are selected from 10mil thick MELINEX® 329 or KAPTON®, which are coated with 50±4 nm goldwithin-lot C.V. of <5% by: Techni-Met Advanced Depositions, Inc.,Windsor, Conn., USA. It is appreciated that the base 212 may be eitherpurchased pre-coated with conductive material 216 or may be coated bysputtering or vapor deposition, in accordance with this disclosure. Itis further appreciated that the thickness of the conductive material canvary in accordance with this disclosure.

Spacer 214 is illustratively positioned on the top surface 232 of thebase 212 adjacent to end 224. Spacer 214 has an upper surface 236 and alower surface 238 (FIG. 9) facing the base 212. Referring now to FIG. 2,the spacer 214 has edges 240, 242, 244, 246. Illustratively, spacer 214has a length of about 6 mm, a width of about 10 mm and a height of about4 mil. It is appreciated, however that these values are merelyillustrative and that the biosensor may be formed without a spacer andthat the dimensions of the spacer 214 may vary in accordance with thepresent disclosure.

Spacer 214 is formed from an insulating material, so that it will notprovide an electrical connection between electrodes formed from theconductive material 216. Non-limiting examples of suitable insulatingmaterials include glass, ceramics, polymers, photoimageable coverlaymaterials, and photoresists—non-limiting examples of which are disclosedin U.S. patent application Ser. No. 10/264,891, filed Oct. 4, 2002, thedisclosure of which is incorporated herein by reference. Illustratively,spacer 214 is formed of 4 mil MELINEX® polyester film, which ispreferred for use with whole blood samples. It is appreciated, however,that when the sample is plasma or serum, 1-2 mil film may be preferredfor use in accordance with this disclosure. It is appreciated, howeverthat these values are merely illustrative and that the composition anddimension of the spacer 214 may vary in accordance with the desiredheight of the sample-receiving chamber.

A slit 248 is formed in the spacer 214 and extends from the edge 240toward the edge 242. The slit 248 defines at least the length and widthof the sample-receiving chamber 220 and is defined by edges 249.Illustratively, the slit 248 has a length of 5 mm, a width of 1 mm, anda height of 0.1 mm, but may have a variety of lengths and widths inaccordance with the present disclosure. It is further appreciated thatthe edges 249 of the slit may also be curved or angular in accordancewith this disclosure.

As shown in FIG. 1, the cover 218 is positioned on the upper surface 236of spacer 214. Cover 218 has a first surface 250 and a second surface252 (FIG. 9) facing the base 212. Further, the cover 218 has edges 254,256, 258, 260. As shown in FIG. 1, the cover 218 has a length that isless than the length of the slit 248. Illustratively, cover 218 has alength of about 4 mm, a width of about 10 mm and a height of about 0.1mm. It is appreciated, however that these values are merely illustrativeand that the biosensor may be formed without a cover and that thedimensions of the cover 218 may vary in accordance with the presentdisclosure.

The cover 218 is illustratively formed of a clear material having ahydrophilic adhesive layer in proximity to the spacer. Non-limitingexamples of materials suitable for cover 218 include polyethylene,polypropylene, polyvinylchloride, polyimide, glass, or polyester. Apreferred material for cover 218 is 100 μm polyester. A preferredadhesive is ARCare 8586 having a MA-55 hydrophilic coating, commerciallyavailable from Adhesives Research Inc., Glen Rock, Pa. Further, it isappreciated that the cover may have markings in accordance with thisdisclosure.

The slit 248 in the spacer 214, together with the cover 218, and thebase 212, form the sample-receiving chamber 220 (FIG. 9), which acts toexpose reagent 264 to a fluid to be tested from a user of biosensor 210.This sample-receiving chamber 220 can act as a capillary channel,drawing the fluid to be tested from the opening 221 onto a sensingregion of the conductive material 216 and toward a vent 262. It isappreciated that the biosensor may be formed without a spacer inaccordance with this disclosure and that in addition to or instead ofthe spacer and the cover, a variety of dielectric materials may coverthe base 212 exposing only selected portions of the conductive materialin accordance with this disclosure. Moreover, it is appreciated thatwhen present, the dimensions of the channel 220 may vary in accordancewith this disclosure.

FIG. 2 illustrates the conductive material 216 defining electrodesystems comprising a first electrode set 266 and a second electrode set268, and corresponding traces 279, 277 and contact pads 278, 282,respectively. The conductive material 216 may contain pure metals oralloys, or other materials, which are metallic conductors. Preferably,the conductive material is transparent at the wavelength of the laserused to form the electrodes and of a thickness amenable to rapid andprecise processing. Non-limiting examples include aluminum, carbon,copper, chromium, gold, indium tin oxide (ITO), palladium, platinum,silver, tin oxide/gold, titanium, mixtures thereof, and alloys ormetallic compounds of these elements. Preferably, the conductivematerial includes noble metals or alloys or their oxides. Mostpreferably, the conductive material includes gold, palladium, aluminum,titanium, platinum, ITO and chromium. The conductive material ranges inthickness from about 10 nm to 80 nm, more preferably, 30 nm to 70 nm.FIGS. 1-3, 6, and 8-9 illustrate the biosensor 210 with a 50 nm goldfilm. It is appreciated that the thickness of the conductive materialdepends upon the transmissive property of the material and other factorsrelating to use of the biosensor.

Illustratively, the conductive material 216 is ablated into twoelectrode systems that comprise sets 266, 268. In forming these systems,the conductive material 216 is removed from at least about 5% of thesurface area of the base 212, more preferably at least about 50% of thesurface area of the base 212, and most preferably at least about 90% ofthe surface area of the base 212. As shown in FIG. 2, the onlyconductive material 216 remaining on the base 212 forms at least aportion of an electrode system.

While not illustrated, it is appreciated that the resulting patternedconductive material can be coated or plated with additional metallayers. For example, the conductive material may be copper, which isthen ablated with a laser, into an electrode pattern; subsequently, thecopper may be plated with a titanium/tungsten layer, and then a goldlayer, to form the desired electrodes. Preferably, a single layer ofconductive material is used, which lies on the base 212. Although notgenerally necessary, it is possible to enhance adhesion of theconductive material to the base, as is well known in the art, by usingseed or ancillary layers such as chromium nickel or titanium. Inpreferred embodiments, biosensor 210 has a single layer of gold,palladium, platinum or ITO.

As shown in FIGS. 2 and 9, the biosensor 210 includes an electrodesystem comprising at least a working electrode and a counter electrodewithin the sample-receiving chamber 220. The sample-receiving chamber220 is configured such that sample fluid entering the chamber is placedin electrolytic contact with both the working electrode and the counterelectrode. This allows electrical current to flow between the electrodesto effect the electrooxidation or electroreduction of the analyte or itsproducts.

Referring now to FIG. 3, the first electrode set 266 of the electrodesystem includes two electrodes 270, 272. Illustratively, electrode 270is a working electrode and electrode 272 is a counter electrode. Theelectrodes 270, 272 each have a single element or finger 280 that is incommunication with a contact pad 278 via a connecting trace 279 (shownin FIG. 2). The electrode fingers 280 of the electrodes 270, 272cooperate to define an electrode pattern formed as a macroelectrodearray. It is appreciated, as will be discussed hereafter, that theelectrodes 270, 272 can include more than one finger each in accordancewith this disclosure. It is further appreciated that the shape, size andrelative configuration of the electrodes fingers may vary in accordancewith the present disclosure.

As shown in FIG. 2, the second electrode set 268 includes two electrodes274, 276. Illustratively, electrode 274 is a working electrode andelectrode 276 is a counter electrode. Further, the electrodes 274, 276each have five electrode elements or fingers 284 that are incommunication with a contact pad 282 via a connecting trace 277.Referring now to FIG. 3, the electrode fingers 284 cooperate to definean electrode pattern formed as an interlaced microelectrode array. Whilefive electrode fingers 284 are illustrated, it is appreciated that theelements of electrodes 274, 276 can each be formed with greater or fewerthan five electrode fingers in accordance with this disclosure. It isfurther appreciated that the shape, size and relative configuration ofthe electrodes may vary in accordance with the present disclosure.

It is appreciated that the values for the dimensions of the electrodesets 266, 268 as illustrated in FIG. 2 are for a single specificembodiment, and these values may be selected as needed for the specificuse. For example, the length of the electrode sets may be any length, upto the length of the base depending upon the orientation of theelectrode sets on the base. Further, it is appreciated that the width ofthe conducting traces in communication with the electrode sets may vary,a non-limiting example of which is from about 0.4 mm to about 5 mm. Itis further appreciated that the width of each contact pad may vary, anon-limiting example of which is from about 1 mm to about 5 mm. Theelectrode patterns shown in FIG. 2 are symmetric, however this is notrequired, and irregular or asymmetric patterns (or electrode shapes) arepossible in accordance with this disclosure. Further, the number ofelectrode sets on the base 212 may vary, and therefore each base 212 cancontain, for example 1 to 1000 electrode sets, preferably 2 to 20electrode sets, more preferably 2 to 3 electrode sets.

Referring again to the first electrode set 266 of FIG. 3, each electrodefinger 280 is defined by an inner edge 281, an outer edge 283, andopposite third and fourth edges 285, 287. Each edge 218, 283, 285, 287has a smooth edge quality. As discussed earlier, the edge quality of theelectrodes 270, 272 is defined by the edge's deviation from a lineextending between first and second points. The following description ofdeviations can apply to each edge of electrodes 270, 272 of biosensor210. For clarity purposes, however, only the edge 281 of electrode 270will be discussed hereafter.

As shown in FIG. 3, the edge 281 of electrode 270 extends between points289, 291 located on the base 212. For illustrative purposes only, points289, 291 are located at opposite ends of the inner edge 281. It isappreciated that the points 289, 291 may be positioned at a variety oflocations and at a variety of distances relative to one anotherdepending upon the length of the desired edge in accordance with thisdisclosure.

As shown in FIG. 4, a line 293 extends exactly between points 289, 291.A standard deviation of the edge 281 (as shown by arrow 295) from theline 293 is less than about 6 μm in accordance with this disclosure,creating an edge with a smooth edge quality. In preferred embodiments,the standard deviation of the edge from the line 293 is less than 2 μm,and most preferably less than 1.0 μm. An example of this deviation frommean is illustrated in FIG. 10. Further, a photograph of an edge with asmooth edge quality is shown in FIG. 22.

The edge quality illustrated in FIG. 10 was measured using Micro-Measuresystem commercially available from LPKF Laser Electronic GmbH, ofGarbsen, Germany with Metric 6.21 software. The Metric software allowsthe display and measuring of video images on the PC. Measurements weremade by capturing the image and then allowing the software to place a 10μm grid over the image. Measurements of the width were made at 10 μmintervals along the length of a line 250 μm using a point-to-pointprocess. The effective video magnification to video screen was 575X.(Using objective Q750). Video magnification=Actual measured “Scalelength” on the video screen (μm)/Scale value (μm). For example, 115000μm/200 μm=575X.

Further, the deviation from mean of the edges illustratedphotographically by FIGS. 21 and 22 was measured using a QVH-606 PROVision Measuring System (computer-controlled non-contact measurementsystem), commercially available from Mitutoyo America Corporation,Aurora, Ill. with an effective magnification to video screen=470X.Standard deviations were calculated from measurements made at an averageinterval of 0.69 μm for a length of at least 250 μm. Other settings:Ring lighting (Intensity 89, Position 60), Edge Detection (EdgeSlope=Falling, Edge Detection TH=169, THS=18.5, THR=0.5 ScanInterval=1). The deviation from mean of the edge of FIG. 21 was plottedand found to be greater than 6 μm. Referring to FIG. 22, the deviationfrom mean was plotted for the edge and found to be less than about 2 μm.

Referring again to FIG. 4, the line 293 is illustratively a straightline. It is appreciated, however, that the shape of the line 293 isunimportant as it may be curved or angular, so long as the standarddeviation of the edge 281 from that line 293 is less than about 6 μm. Itis also appreciated, as discussed above, that the specific positions offirst and second locations 289, 291 on the surface 232 may vary inaccordance with the disclosure depending upon the desired length of theelectrode edge.

The electrode fingers 280, as shown in FIG. 3, are separated from oneanother by an electrode gap 286, which corresponds to the feature sizeof the electrode pattern of the electrode set 266. The electrode gap 286relates to the smallest dimension of space between the adjacent edges281 of electrode fingers 280. Illustratively, in biosensor 210, theelectrically insulative material of the top surface 232 is exposedbetween the electrode fingers 280 along a length 290. It is appreciated,however, that rather than top surface 232 being exposed, the base can becoated with materials, or recesses can be formed between the electrodesas disclosed in U.S. Pat. No. 6,540,890, the disclosure of which isincorporated herein by reference.

As shown in FIGS. 3 and 5, the inner edges 281 of electrode fingers 280have an equal length, illustrated by the numeral 290 and are separatedfrom one another by the electrode gap 286. Illustratively, the electrodegap 286 has a width of about 100 μm to about 250 μm, more specificallythe width is about 250 μm. As shown in FIG. 3, the gap 286 has apre-determined width value along a length 290 of the opposing edges 281of the electrode fingers 280. A standard deviation (as shown by arrow292 in FIG. 5) of the gap 286 from the width value is less than 6 μm,preferably less than 2 μm, and most preferably less than 1.0 μm.Further, the smoothness standard deviation for macroelectrodes ispreferably less than about 2% of the gap between adjacent macroelectrodeelements, more preferably less than about 1% of the gap 286.

The electrode fingers 284, which define the elements of electrodes 274,276 are illustrated in FIGS. 3 and 6. For clarity purposes, however,only three of these electrode fingers 284 will be discussed hereafter asthey are illustrated in FIG. 6. Each electrode finger 284 is defined bya first edge 296 and a second edge 297. Further, adjacent fingers 284have spaced-apart third and fourth edges 298, 299 respectively. Theseedges 296, 297, 298, 299 of fingers 284 can also have a smooth edgequality. As previously described with reference to electrodes 270, 272,the edge quality of the electrodes 274, 276 is defined by the respectiveedge's deviation from a line extending between first and second points.The following description of deviations will apply to each edge ofelectrode fingers 284 of biosensor 210. For clarity purposes, however,only one edge 296 of electrode finger 284 will be discussed hereafter.

The edge 296 of electrode finger 284 extends between first and secondpoints 301, 302 located on the base 212. As shown in FIG. 7, a line 300extends exactly between points 301, 302. A standard deviation of theedge 296 (as shown by arrow 295) from the line 300 is less than about 6μm, in accordance with this disclosure, creating an edge with a smoothedge quality. In preferred embodiments, the standard deviation of theedge from the line 300 is less than 2 μm, and most preferably less than1.0 μm. Illustratively, the line 300 is a straight line. It isappreciated, however, that the shape of the line 300 is unimportant asit may be curved or angular. It is also appreciated that the specificpositions of first and second locations 300, 301 on the surface 232 mayvary in accordance with the disclosure.

Referring again to FIG. 3, the electrode fingers 284 are separated fromone another by an electrode gap 288, which corresponds to the featuresize of the electrode pattern of the electrode set 268. The electrodegap 288 relates to the smallest dimension of space between adjacentedges 296, 297 of fingers 284. Illustratively, in biosensor 210, theelectrically insulative material of the base 212 is exposed between theelectrode fingers 284 along a length 303. It is appreciated, however,that rather than top surface 232 being exposed, the base can be coatedwith materials, or recesses can be formed between the electrodes asdisclosed in U.S. Pat. No. 6,540,890, the disclosure of which isincorporated herein by reference.

The electrode gap 288, which corresponds to the feature size of theelectrode pattern of the electrode set 268 is different than the featuresize of the electrode pattern of the electrode set 266. Illustratively,the feature size, or gap 288 between the electrode fingers 284 has awidth of about 100 μm or less, including about 1 μm to about 100 μm,even more preferably 75 μm or less, including about 17 μm to about 50μm. It is appreciated that the electrode gap for a microelectrode arraycan vary. For example, it is understood that the electrode gap can beless than 1 μm in accordance with the present disclosure. The size ofthe achievable gap is dependent upon the quality of the optics, thewavelength of the laser, and the window size of a mask field.

As illustrated in FIG. 3, the gap 288 has a pre-determined width valuealong a length 303 of the opposing edges 296, 297 of the electrodefingers 284. A standard deviation of the gap 288 from the width value isless than 6 μm, preferably less than 2 μm, and most preferably less than1.0 μm. It is appreciated that if the microelements are spaced apart byless than 2 μm, then the smoothness standard deviation is preferablyless than one half, and more preferably less than one fourth, thefeature size of the microelement pattern. In general, the smoothnessstandard deviation for microelectrodes is preferably less than about 5%of the gap between adjacent microelements or feature size, morepreferably less than about 2% of the gap or feature size.

Referring now to FIG. 9, the electrode fingers 284 are covered with thereagent 264 and may be used to provide electrochemical probes forspecific analytes. The starting reagents are the reactants or componentsof the reagent, and are often compounded together in liquid form beforeapplication to the ribbons or reels, or in capillary channels on sheetsof electrodes. The liquid may then evaporate, leaving the reagent insolid form. The choice of a specific reagent depends on the specificanalyte or analytes to be measured, and is not critical to the presentinvention. Various reagent compositions are well known to those ofordinary skill in the art. It is also appreciated that the placementchoice for the reagent on the base may vary and depends on the intendeduse of the biosensor. Further, it is appreciated that the techniques forapplying the reagent onto the base may vary, for example it is withinthe scope of the present disclosure to have the reagent screen-printedonto the fingers.

A non-limiting example of a dispensable reagent for measurement ofglucose in a human blood sample contains 62.2 mg polyethylene oxide(mean molecular weight of 100-900 kilodaltons), 3.3 mg NATROSOL 250 M,41.5 mg AVICEL RC-591 F, 89.4 mg monobasic potassium phosphate, 157.9 mgdibasic potassium phosphate, 437.3 mg potassium ferricyanide, 46.0 mgsodium succinate, 148.0 mg trehalose, 2.6 mg TRITON X-100 surfactant,and 2,000 to 9,000 units of enzyme activity per gram of reagent. Theenzyme is prepared as an enzyme solution from 12.5 mg coenzyme PQQ and1.21 million units of the apoenzyme of quinoprotein glucosedehydrogenase, forming a solution of quinoprotein glucose dehydrogenase.This reagent is further described in U.S. Pat. No. 5,997,817, thedisclosure of which is expressly incorporated herein by reference.

A non-limiting example of a dispensable reagent for measurement ofhematocrit in a sample contains oxidized and reduced forms of areversible electroactive compound (potassium hexacyanoferrate (III)(“ferricyanide”) and potassium hexacyanoferrate (II) (“ferrocyanide”),respectively), an electrolyte (potassium phosphate buffer), and amicrocrystalline material (Avicel RC-591F—a blend of 88%microcrystalline cellulose and 12% sodium carboxymethyl-cellulose,available from FMC Corp.). Concentrations of the components within thereagent before drying are as follows: 400 millimolar (mM) ferricyanide,55 mM ferrocyanide, 400 mM potassium phosphate, and 2.0% (weight:volume) Avicel. A further description of the reagent for a hematocritassay is found in U.S. Pat. No. 5,385,846, the disclosure of which isexpressly incorporated herein by reference.

Non-limiting examples of enzymes and mediators that may be used inmeasuring particular analytes in biosensors of the present invention arelisted below in Table 1. TABLE 1 Mediator Analyte Enzymes (OxidizedForm) Additional Mediator Glucose Glucose Dehydrogenase Ferricyanide andDiaphorase Osmium complexes, nitrosoanaline complexes GlucoseGlucose-Dehydrogenase Ferricyanide (Quinoprotein) CholesterolCholesterol Esterase and Ferricyanide 2,6-Dimethyl-1,4- CholesterolOxidase Benzoquinone 2,5-Dichloro-1,4- Benzoquinone or PhenazineEthosulfate HDL Cholesterol Esterase Ferricyanide 2,6-Dimethyl-1,4-Cholesterol and Cholesterol Oxidase Benzoquinone 2,5-Dichloro-1,4-Benzoquinone or Phenazine Ethosulfate Triglycerides Lipoprotein Lipase,Ferricyanide or Phenazine Methosulfate Glycerol Kinase, and PhenazineGlycerol-3-Phosphate Ethosulfate Oxidase Lactate Lactate OxidaseFerricyanide 2,6-Dichloro-1,4- Benzoquinone Lactate LactateDehydrogenase Ferricyanide and Diaphorase Phenazine Ethosulfate, orPhenazine Methosulfate Lactate Diaphorase Ferricyanide PhenazineEthosulfate, or Dehydrogenase Phenazine Methosulfate Pyruvate PyruvateOxidase Ferricyanide Alcohol Alcohol Oxidase Phenylenediamine BilirubinBilirubin Oxidase 1-Methoxy- Phenazine Methosulfate Uric Acid UricaseFerricyanide

In some of the examples shown in Table 1, at least one additional enzymeis used as a reaction catalyst. Also, some of the examples shown inTable 1 may utilize an additional mediator, which facilitates electrontransfer to the oxidized form of the mediator. The additional mediatormay be provided to the reagent in lesser amount than the oxidized formof the mediator. While the above assays are described, it iscontemplated that current, charge, impedance, conductance, potential, orother electrochemically indicated property of the sample might beaccurately correlated to the concentration of the analyte in the samplewith biosensors in accordance with this disclosure.

Another non-limiting example of a suitable dispensable reagent for usewith biosensors of the present invention is nitrosoanaline reagent,which includes a PQQ-GDH and para-Nitroso-Aniline mediator. A protocolfor the preparation of the nitrosoanaline reagent is the same in allrespects as disclosed in U.S. Patent Application Ser. No. 60/480,298,filed Jun. 20, 2003, “System And Method For Analyte Measurement Using ACExcitation”, filed Jun. 20, 2003, the disclosure of which isincorporated herein by reference. The reagent mass composition—prior todispensing and drying is as set forth in Table 2. TABLE 2 Mass forComponent % w/w 1 kg solid Polyethylene oxide (300 KDa) 0.8054% 8.0539 gsolid NATROSOL ® 250 M 0.0470% 0.4698 g solid AVICEL ® RC-591F 0.5410%5.4104 g solid Monobasic potassium phosphate 1.1437% 11.4371 g(anhydrous) solid Dibasic potassium 1.5437% 15.4367 g phosphate(anhydrous) solid Sodium Succinate hexahydrate 0.5876% 5.8761 g solidPotassium Hydroxide 0.3358% 3.3579 g solid Quinoprotein glucosedehydrogenase 0.1646% 1.6464 g (EncC#: 1.1.99.17) solid PQQ 0.0042%0.0423 g solid Trehalose 1.8875% 18.8746 g solid Mediator BM 31.11440.6636% 6.6363 g solid TRITON ® X-100 0.0327% 0.3274 g solvent Water92.2389% 922.3888 g % Solids 0.1352687 Target pH 6.8 Specific EnzymeActivity Used (U/mg 689 DCIP Dispense Volume per Biosensor 4.6 mg

Biosensor 210 is illustratively manufactured using two apparatuses 10,10′, shown in FIGS. 17-18 and 19, respectively. It is appreciated thatunless otherwise described, the apparatuses 10, 10′ operate in a similarmanner. Referring first to FIG. 17, biosensor 210 is manufactured byfeeding a roll of ribbon 20 having an 80 nm gold laminate, which isabout 40 mm in width, into a custom fit broad field laser ablationapparatus 10. The apparatus 10 comprises a laser source 11 producing abeam of laser light 12, a chromium-plated quartz mask 14, and optics 16.It is appreciated that while the illustrated optics 16 is a single lens,optics 16 is preferably a variety of lenses that cooperate to make thelight 12 in a pre-determined shape.

A non-limiting example of a suitable ablation apparatus 10 (FIGS. 17-18)is a customized MicrolineLaser 200-4 laser system commercially availablefrom LPKF Laser Electronic GmbH, of Garbsen, Germany, which incorporatesan LPX-400, LPX-300 or LPX-200 laser system commercially available fromLambda Physik AG, Gottingen, Germany and a chromium-plated quartz maskcommercially available from International Phototool Company, ColoradoSprings, Colo.

For the MicrolineLaser 200-4 laser system (FIGS. 17-18), the lasersource 11 is a LPX-200 KrF-UV-laser. It is appreciated, however, thathigher wavelength UV lasers can be used in accordance with thisdisclosure. The laser source 11 works at 248 nm, with a pulse energy of600 mJ, and a pulse repeat frequency of 50 Hz. The intensity of thelaser beam 12 can be infinitely adjusted between 3% and 92% by adielectric beam attenuator (not shown). The beam profile is 27×15 mm²(0.62 sq. inch) and the pulse duration 25 ns. The layout on the mask 14is homogeneously projected by an optical elements beam expander,homogenizer, and field lens (not shown). The performance of thehomogenizer has been determined by measuring the energy profile. Theimaging optics 16 transfer the structures of the mask 14 onto the ribbon20. The imaging ratio is 2:1 to allow a large area to be removed on theone hand, but to keep the energy density below the ablation point of theapplied chromium mask on the other hand. While an imaging of 2:1 isillustrated, it is appreciated that the any number of alternative ratiosare possible in accordance with this disclosure depending upon thedesired design requirements. The ribbon 20 moves as shown by arrow 25 toallow a number of layout segments to be ablated in succession.

The positioning of the mask 14, movement of the ribbon 20, and laserenergy are computer controlled. As shown in FIG. 17, the laser beam 12is projected onto the ribbon 20 to be ablated. Light 12 passing throughthe clear areas or windows 18 of the mask 14 ablates the metal from theribbon 20. Chromium coated areas 24 of the mask 14 blocks the laserlight 12 and prevent ablation in those areas, resulting in a metallizedstructure on the ribbon 20 surface. Referring now to FIG. 18, a completestructure of electrical components may require additional ablation stepsthrough a second mask 14′. It is appreciated that depending upon theoptics and the size of the electrical component to be ablated, that onlya single ablation step or greater than two ablation steps may benecessary in accordance with this disclosure. Further, it is appreciatedthat instead of multiple masks, that multiple fields may be formed onthe same mask in accordance with this disclosure.

Specifically, a second non-limiting example of a suitable ablationapparatus 10′ (FIG. 19) is a customized laser system commerciallyavailable from LPKF Laser Electronic GmbH, of Garbsen, Germany, whichincorporates a Lambda STEEL (Stable energy eximer laser) laser systemcommercially available from Lambda Physik AG, Göttingen, Germany and achromium-plated quartz mask commercially available from InternationalPhototool Company, Colorado Springs, Colo. The laser system features upto 1000 mJ pulse energy at a wavelength of 308 nm. Further, the lasersystem has a frequency of 100 Hz. The apparatus 10′ may be formed toproduce biosensors with two passes as shown in FIGS. 17 and 18, butpreferably its optics permit the formation of a 10×40 mm pattern in a 25ns single pass, or a single pulse of a laser beam from the laserapparatus.

While not wishing to be bound to a specific theory, it is believed thatthe laser pulse or beam 12 that passes through the mask 14, 14′, 14″ isabsorbed within less than 1 μm of the surface 232 on the ribbon 20. Thephotons of the beam 12 have an energy sufficient to causephoto-dissociation and the rapid breaking of chemical bonds at themetal/polymer interface. It is believed that this rapid chemical bondbreaking causes a sudden pressure increase within the absorption regionand forces material (metal film 216) to be ejected from the polymer basesurface. Since typical pulse durations are around 20-25 nanoseconds, theinteraction with the material occurs very rapidly and thermal damage toedges of the conductive material 216 and surrounding structures isminimized. The resulting edges of the electrical components have highedge quality and accurate placement as contemplated by the presentinvention.

Fluence energies used to remove or ablate metals from the ribbon 20 aredependent upon the material from which the ribbon 20 is formed, adhesionof the metal film to the base material, the thickness of the metal film,and possibly the process used to place the film on the base material,i.e. supporting and vapor deposition. Fluence levels for gold onKALADEX® range from about 50 to about 90 mJ/cm², on polyimide about 100to about 120 mJ/cm², and on MELINEX® about 60 to about 120 mJ/cm². It isunderstood that fluence levels less than or greater than the abovementioned can be appropriate for other base materials in accordance withthe disclosure.

Patterning of areas of the ribbon 20 is achieved by using the masks 14,14′. Each mask 14, 14′ illustratively includes a mask field 22containing a precise two-dimensional illustration of a pre-determinedportion of the electrode component patterns to be formed. FIG. 17illustrates the mask field 22 including contact pads and a portion oftraces. As shown in FIG. 18, the second mask 14′ contains a secondcorresponding portion of the traces and the electrode patternscontaining fingers. As previously described, it is appreciated thatdepending upon the size of the area to be ablated, the mask 14 cancontain a complete illustration of the electrode patterns (FIG. 19), orportions of patterns different from those illustrated in FIGS. 17 and 18in accordance with this disclosure. Preferably, it is contemplated thatin one aspect of the present invention, the entire pattern of theelectrical components on the test strip are laser ablated at one time,i.e., the broad field encompasses the entire size of the test strip(FIG. 19). In the alternative, and as illustrated in FIGS. 17 and 18,portions of the entire biosensor are done successively.

While mask 14 will be discussed hereafter, it is appreciated that unlessindicated otherwise, the discussion will apply to masks 14′, 14″ aswell. Referring to FIG. 17, areas 24 of the mask field 22 protected bythe chrome will block the projection of the laser beam 12 to the ribbon20. Clear areas or windows 18 in the mask field 22 allow the laser beam12 to pass through the mask 14 and to impact predetermined areas of theribbon 20. As shown in FIG. 17, the clear area 18 of the mask field 22corresponds to the areas of the ribbon 20 from which the conductivematerial 216 is to be removed.

Further, the mask field 22 has a length shown by line 30 and a width asshown by line 32. Given the imaging ratio of 2:1 of the LPX-200, it isappreciated that the length 30 of the mask is two times the length of alength 34 of the resulting pattern and the width 32 of the mask is twotimes the width of a width 36 of the resulting pattern on ribbon 20. Theoptics 16 reduces the size of laser beam 12 that strikes the ribbon 20.It is appreciated that the relative dimensions of the mask field 22 andthe resulting pattern can vary in accordance with this disclosure. Mask14′ (FIG. 18) is used to complete the two-dimensional illustration ofthe electrical components.

Continuing to refer to FIG. 1 7, in the laser ablation apparatus 10 theexcimer laser source 11 emits beam 12, which passes through thechrome-on-quartz mask 14. The mask field 22 causes parts of the laserbeam 12 to be reflected while allowing other parts of the beam to passthrough, creating a pattern on the gold film where impacted by the laserbeam 12. It is appreciated that ribbon 20 can be stationary relative toapparatus 10 or move continuously on a roll through apparatus 10.Accordingly, non-limiting rates of movement of the ribbon 20 can be fromabout 0 m/min to about 100 m/min, more preferably about 30 m/min toabout 60 m/min. It is appreciated that the rate of movement of theribbon 20 is limited only by the apparatus 10 selected and may wellexceed 100 m/min depending upon the pulse duration of the laser source11 in accordance with the present disclosure.

Once the pattern of the mask 14 is created on the ribbon 20, the ribbonis rewound and fed through the apparatus 10 again, with mask 14′ (FIG.18). It is appreciated, that alternatively, laser apparatus 10 could bepositioned in series in accordance with this disclosure. A detaileddescription of the step and repeat process is found in U.S. ApplicationSer. No. 60/480,397, filed Jun. 20, 2003, entitled “Devices And MethodsRelating To Analyte Sensors”, the disclosure of which is incorporatedherein by reference. Thus, by using masks 14, 14′, large areas of theribbon 20 can be patterned using step-and-repeat processes involvingmultiple mask fields 22 in the same mask area to enable the economicalcreation of intricate electrode patterns and other electrical componentson a substrate of the base, the precise edges of the electrodecomponents, and the removal of greater amounts of the metallic film fromthe base material.

FIG. 20 is a non-limiting schematic of an electrode set ribbon 124formed in accordance with the present disclosure, although having anelectrode pattern different from that illustrated in FIGS. 17 and 18.The ribbon 124 includes a plurality of panels 120, each of whichincludes a plurality of electrode systems 116. Each system includes twoelectrodes 104 and 104 having a sensing region 110. Also shown is theoriginal metallic laminate ribbon 122 that is subject to laser ablationto form the electrode set ribbon 124. The width of the ribbon 122 isselected to accommodate the laser ablation system 10, 10′, and may be,for example, 40 to 0.4 inches (1.2 m to 10.25 mm). The ribbon may be anylength, and is selected based on the desired number of electrode sets,and/or the ease of handling and transport of the ribbons. The size ofeach individual panel is selected to fit conveniently on the ribbon, andtherefore each panel may contain I to 1000 electrode sets, preferably 2to 20 electrode sets.

Once the complete electrode patterns are created, it is appreciated thatthe ribbon 20 may be coupled to a spacer and a cover using any number ofwell-known commercially available methods. A non-limiting example of asuitable method of manufacture, is described in detail in U.S.Application Ser. No. 60/480,397, filed Jun. 20, 2003, entitled “DevicesAnd Methods Relating To Analyte Sensors”, the disclosure of which isincorporated herein by reference. In summary, however, it is appreciatedthat a reagent is placed upon the ribbon and dried conventionally withan in-line drying system. The rate of processing is nominally 30-38meters per minute and depends upon the rheology of the reagent. Reagentssuitable for the biosensor 210 are given above, but a preferable reagentis set out in Table 2.

The materials are processed in continuous reels such that the electrodepattern is orthogonal to the length of the reel, in the case of thebase. The spacer material is laminated onto the coated ribbon 20. Priorto laminating the spacer material, however, a portion of the spacermaterial is removed, thereby forming a slit. A punching process is usedto remove the unneeded portion of the spacer. The die set governs theshape of the slit. The resulting slit-spacer is placed in a reel-to-reelprocess onto the base. A cover is then laminated onto the spacer using areel-to reel process. The biosensors can then be produced from theresulting reels of material by means of slitting and cutting.

The slit in the spacer preferably forms a capillary fill space betweenthe base and the cover. A hydrophobic adhesive on the spacer preventsthe test sample from flowing into the reagent under the spacer andtherefore the fill space defines the test chamber volume. It isappreciated that the chamber volume can vary in accordance with thisdisclosure depending upon the application of the biosensor. Anon-limiting detailed description of suitable fill volumes is found inU.S. Application Ser. No. 60/480,397, filed Jun. 20, 2003, entitled“Devices And Methods Relating To Analyte Sensors”, the disclosure ofwhich is incorporated herein by reference.

As discussed above, biosensor 210 has two electrode patterns havingdifferent feature sizes on a common planar surface and thus achievesmultiple functionalities on that surface. Preferably, electrode set 266has an electrode pattern formed as a macro electrode array with a firstpre-defined feature size. A non-limiting example of a suitablefunctionality of the macroelectrode array is hematocrit levelcorrection, which is described in U.S. Patent Application Ser. No.60/480,298, filed Jun. 20, 2003, entitled “System And Method For AnalyteMeasurement Using AC Excitation” and “U.S. Application Ser. No.60/480,397; filed Jun. 20, 2003, entitled “Devices And Methods RelatingTo Analyte Sensors”, respectively, the disclosures of which areincorporated herein by reference. It is appreciated that during use, atest meter (not shown) applies a voltage to one electrode and measuresthe current response at the other electrode to obtain a signal asdescribed in U.S. Application Ser. No. 60/480,298, filed Jun. 20, 2003,entitled “System and Method For Analyte Measurement Using ACExcitation”.

Electrode set 268 has an electrode pattern formed as an interlacedmicroelectrode array with a second pre-defined feature size. Anon-limiting example of a suitable functionality of the microelectrodearray is glucose estimation, which is also described in U.S. PatentApplication Ser. No. 60/480,298, filed Jun. 20, 2003, entitled “SystemAnd Method For Analyte Measurement Using AC Excitation”, the disclosureof which is incorporated herein by reference. Further, it is appreciatedthat during use, a test meter (not shown) applies a voltage to oneelectrode and measures the current response at the other electrode toobtain a signal as described in U.S. Patent Application Ser. No.60/480,298, filed Jun. 20, 2003, entitled “System and Method For AnalyteMeasurement Using AC Excitation”, the disclosure of which isincorporated herein by reference.

In operation, a user places their lanced finger at opening 221 ofbiosensor 210. A liquid sample (whole blood) flows from the finger intothe opening 221. The liquid sample is transported via capillary actionthrough the sample-receiving chamber 220 and across the fingers 280 ofthe element of the electrode set 266. Subsequently, the liquid sampleflows through the sample-receiving chamber 220 toward vent 262 and intoengagement with the reagent 264 situated upon the fingers 284 of theelement of the electrode set 268. As discussed above, hematocritcorrection values are determined from the interaction of the liquidsample with the fingers 280 and a glucose determination from theinteraction of the liquid sample/reagent mixture with the fingers 284.While hematocrit and glucose determination functionalities are describedwith reference to biosensor 210, it is appreciated that the electrodepatterns, may be used for a variety of functionalities in accordancewith the present disclosure.

The processes and products described include disposable biosensors,especially for use in diagnostic devices. However, also included areelectrochemical biosensors for non-diagnostic uses, such as measuring ananalyte in any biological, environmental, or other, sample. In addition,it is appreciated that various uses and available functions of thebiosensor may stand alone or be combined with one another in accordancewith this disclosure.

As discussed below with reference to FIGS. 11-16, each of the disclosedbiosensors operates from the standpoint of a user in a manner similar tothat described above with reference from 210. In addition, likecomponents of the biosensors are numbered alike.

Referring now to FIG. 11, a biosensor 310 is formed and manufactured ina manner similar to biosensor 210 except for the pattern of theconductive material 216 positioned on the base 212. The conductivematerial 216 of biosensor 310 defines a first electrode system 366 and asecond electrode system 368. The electrode systems 366, 368 are similarto the systems of biosensor 210 except for the resulting pattern of theconnecting traces 377, 379 and contact pads 378, 383 on the base 212. Itis submitted that the traces 377, 379 and pads 378, 383 may take on avariety of shapes and sizes in accordance with this disclosure.

As shown in FIG. 12, a biosensor 510 is formed in a manner similar tobiosensor 210 except for the pattern of the conductive material 216positioned on the base 212. In addition to electrode set 268, theconductive material 216 of biosensor 510 defines a first electrode set566. The electrode set 566 is similar to set 366 except for theconfiguration of the interlacing electrode pattern formed by theelements of the electrodes.

Specifically, the first electrode set 566 includes a working electrodehaving an element with one electrode finger 581 and a counter electrodehaving a element with two electrode fingers 580. The fingers 580, 581cooperate with one another to create an interlaced electrode patternconfigured as a macroelectrode array having a feature size or gap widthof about 250 μm. The electrodes 580, 581 each have an electrode width ofabout 250 μm. As discussed above with set 266, the electrode and gapwidths may vary in accordance with this disclosure.

As described above with reference to biosensor 210, the first and secondelectrode sets 566, 268 have different feature sizes and are used tocreate different functionalities on biosensor 510. A non-limitingexample of a suitable functionality of the first electrode set 566 isfor determining correction factors for hematocrit levels. Themeasurement methods are as discussed above with reference to biosensor210.

Referring now to FIG. 13, a biosensor 610 is formed in a manner similarto biosensor 210 except for the pattern of the conductive material 216positioned on the base 212. In addition to the first electrode set 566as discussed above, the conductive material 216 of biosensor 610 definesa second electrode set 668 spaced-apart from set 566.

The electrode set 668 is similar to set 268 except for the pattern ofinterlacing electrode pattern in the element of the electrodes.Specifically, the second electrode set 668 includes a working electrodeand a counter electrode, each having an element with three electrodefingers 661. The fingers 661 cooperate with one another to define aninterlaced electrode pattern configured as a microelectrode array havinga feature size or gap width of about 50 μm, which is less than thefeature size of the electrode pattern of the set 566. The electrodes 661each have an electrode width of about 50 μm. As discussed above with set268, the electrode and gap widths may vary in accordance with thisdisclosure.

In addition, biosensor 610 includes a reagent 664. Reagent 664 issimilar to reagent 264, and only differs in its width as it is appliedonto the base 212. Specifically, the reagent 664 extends acrosselectrode fingers 661. A non-limiting example of a suitablefunctionality of the second electrode set 668 is a glucose determinationfunctionality. The measurement methods are as discussed above withreference to biosensor 210.

As shown in FIG. 14, a biosensor 710 is formed in a manner similar tobiosensor 210 except for the pattern of the conductive material 216positioned on the base 212. The conductive material 216 of biosensor 710defines the first electrode set 366 as discussed above and a secondelectrode set 768. The electrode set 768 is similar to set 268 exceptfor the pattern of an interlacing electrode pattern formed by theelement of the electrodes. Specifically, the second electrode set 768includes a working electrode and a counter electrode, each havingelement with five electrode fingers 770. The fingers 770 cooperate withone another to define an interlaced electrode pattern configured as amicroelectrode array having a feature size or gap width of about 30 μm,which is less than the feature size of electrode pattern of set 366. Theelectrode fingers 770 each have an electrode width of about 50 μm. Asdiscussed above with set 266, the electrode and gap widths may vary inaccordance with this disclosure. A non-limiting example of a suitablefunctionality of the second electrode set 668 is a glucose determinationfunctionality. The measurement methods are as discussed above withreference to biosensor 210.

In addition, biosensor 710 includes a reagent 364 that is dispensed uponthe fingers 770. It is appreciated that a variety of dispensing methodsare well known to those skilled in the art. Reagent 364 is preferablythe reagent set forth in Table 2. Moreover, it is appreciated that avariety of reagents, non-limiting examples of which have been discussedabove, may be used in accordance with this disclosure.

FIG. 15 illustrates a biosensor 1310 in accordance with this disclosure.Biosensor 1310 is formed in a manner similar to biosensor 210 except forthe configuration of the conductive material 216 positioned on the base212, the cover 1118, and the spacer I 114. The cover 1118 and spacer1114 are similar to cover 218 and spacer 214 except for their dimensionsrelative to the base 212 as shown in FIG. 15. The conductive material216 of biosensor 1310 defines a first electrode set 1366 and a secondelectrode set 1368. The first electrode set 1366 includes a workingelectrode and a counter electrode, each having five electrode fingers1370. The fingers 1370 cooperate with one another to define aninterlaced electrode pattern formed as a microelectrode array having afeature size or gap width of about 17 μm. The electrode fingers 1370each have an electrode width of about 20 μm.

The second electrode set 1368 includes a working electrode and a counterelectrode, each having three electrode fingers 1371. The electrodefingers 1371 cooperate with one another to define an interlacedelectrode pattern formed as a microelectrode array having a feature sizeor gap width of about 10 μm. The electrode fingers 1371 each have anelectrode width of about 20 μm. As discussed above with set 266, theelectrode and gap widths of fingers 1370 and 1371 may vary in accordancewith this disclosure.

The reagent 264 extends across the electrode fingers 1371 of theelectrode set 1368. A non-limiting example of a suitable functionalityof the first electrode set 1366 includes hematocrit correction asdescribed above with reference to biosensor 210. Likewise, anon-limiting example of a suitable functionality of the second electrodeset 1368 is used for determining a glucose estimate as described abovewith reference to biosensor 210. The method of measurement for theelectrode sets, 1366 and 1368 is also as described above with referenceto biosensor 210.

FIG. 16 illustrates biosensor 1510. Biosensor 1510 is identical tobiosensor 210, except for the reagent 1564. Reagent 364 is dispensedonto the electrode fingers 284 as discussed above with reference tobiosensor 710 of FIG. 14.

Although the invention has been described in detail with reference to apreferred embodiment, variations and modifications exist within thescope and spirit of the invention, on as described and defined in thefollowing claims.

1. A method of making a biosensor electrode set, comprising: providing alaser system having a lens and a mask, and ablating through a portion ofa metallic layer with a laser, to form an electrode pattern, the patternof ablation being controlled by the lens and the mask; wherein saidfirst metallic layer is on an insulating substrate.
 2. The method ofclaim 1 wherein said metallic layer comprises copper.
 3. The method ofclaim 1 wherein said metallic layer comprises at least one memberselected from the group consisting of gold, platinum, palladium andiridium.
 4. The method of claim 1 wherein said insulating substrate is apolymer.
 5. The method of claim 1 wherein said pattern has a featuresize of less than 100 μm.
 6. The method of claim 1 wherein said patternhas a feature size of less than 75 μm.
 7. The method of claim 1 whereinsaid pattern has a feature size of 1 μm to 50 μm.
 8. The method of claim1 wherein the pattern is formed as a microelectrode array.
 9. The methodof claim 1 wherein said metallic layer is in contact with saidinsulating substrate.
 10. The method of claim 9 wherein said metalliclayer comprises at least one member selected from the group consistingof gold, platinum, palladium and iridium.
 11. The method of claim 1further comprising the step of applying a second metallic layer on saidmetallic layer.
 12. The method of claim 1 wherein said electrode patternis formed in less than about 0.25 seconds.
 13. The method of claim 1wherein said electrode pattern is formed in less than about 50nanoseconds.
 14. The method of claim 1 wherein said electrode pattern isformed in about 25 nanoseconds.
 15. A method of making an electrode setribbon, comprising: providing a laser system having a lens and a mask,and ablating through a portion of a metallic layer with a laser, to forma plurality of electrode patterns, the pattern of ablation beingcontrolled by the lens and the mask, wherein the metallic layer is on aninsulating substrate, and said electrode set ribbon comprises aplurality of electrode sets.
 16. The method of claim 15 wherein saidmetallic layer comprises at least one member selected from the groupconsisting of gold, platinum, palladium and iridium and said metalliclayer is in contact with said insulating substrate.
 17. The method ofclaim 15 wherein said electrode pattern is formed in less than about 50nanoseconds.
 18. The method of claim 15 wherein said electrode patternis formed in about 25 nanoseconds.
 19. The method of claim 15 wherein atleast one pattern has a feature size of less than 100 μm.
 20. The methodof claim 15 wherein at least one pattern has a feature size of 1 μm to50 μm.
 21. A method of making a sensor strip, comprising: providing alaser system having a lens and a mask, forming an electrode set byablating through a portion of a first metallic layer with a laser, apattern of ablation being controlled by the lens and the mask; whereinsaid first metallic layer is on an insulating substrate, and cuttingsaid substrate, to form a strip.
 22. The method of claim 21 furthercomprising the step of applying a dielectric on a portion of saidmetallic layer.
 23. The method of claim 21 further comprising the stepof applying a reagent on a portion of said electrode set.
 24. The methodof claim 21 wherein said metallic layer comprises at least one memberselected from the group consisting of gold, platinum, palladium andiridium.
 25. The method of claim 21 wherein the electrode set is formedin less than about 50 nanoseconds.
 26. The method of claim 21 whereinthe electrode set is formed in about 25 nanoseconds.
 27. The method ofclaim 21 wherein at least one pattern has a feature size of less than100 μm.
 28. The method of claim 21 wherein at least one pattern has afeature size of 1 μm to 50 μm.
 29. A method of making a biosensorelectrode set, comprising: providing a laser system having a lens and amask, and ablating through a portion of a first metallic layer with alaser, to form an electrode pattern, the pattern of ablation beingcontrolled by the lens and the mask, wherein said metallic layer is onan insulating base.
 30. The method of claim 29 wherein the electrodepattern is formed in less than about 50 nanoseconds.
 31. The method ofclaim 29 wherein said electrode pattern is formed in about 25nanoseconds.
 32. The method of claim 31 wherein the metallic layer isgold.
 33. The method of claim 31 wherein said insulating base is apolymer.
 34. The method of claim 31 wherein said pattern has a featuresize of less than 100 μm.
 35. The method of claim 31 wherein saidpattern has a feature size of less than 75 μm.
 36. The method of claim31 wherein said pattern has a feature size of less than 20 μm.
 37. Amethod of making a biosensor strip, comprising: providing a laser systemhaving at least a laser source and a mask, and forming an electrode setby ablating through a portion of a metallic layer with a laser, apattern of ablation being controlled by the mask, wherein said metalliclayer is on an insulating base.
 38. The method of claim 37 furthercomprising the step of applying a reagent on a portion of said electrodeset.
 39. The method of claim 37 wherein the electrode set is formed inless than about 200 nanoseconds.
 40. The method of claim 37 wherein theelectrode set is formed in less than about 50 nanoseconds.
 41. Themethod of claim 37 wherein the electrode set is formed in about 25nanoseconds.
 42. The method of claim 37 wherein the electrode set isformed by a single pulse of laser light from the laser.
 43. The methodof claim 37 wherein the electrode set is formed by pulses of laser lightfrom the laser.
 44. A method of making a biosensor, the methodcomprising the steps of: providing an electrically conductive materialon a base, and forming a pre-determined electrode pattern on the baseusing laser ablation through a mask, the mask having a mask field withat least one opaque region and at least one window formed to allow alaser beam to pass through the mask and to impact predetermined areas ofthe electrically conductive material.
 45. The method of claim 44 whereinthe windows are configured in a window pattern identical in geometry tothe predetermined electrode pattern.
 46. The method of claim 44 whereinthe electrode set is formed in less than about 200 nanoseconds.
 47. Themethod of claim 44 wherein the electrode set is formed in less thanabout 50 nanoseconds.
 48. The method of claim 44 wherein the electrodeset is formed in about 25 nanoseconds.
 49. The method of claim 44wherein the electrode pattern is formed by a single pulse of laser lightfrom the laser.
 50. The method of claim 44 wherein the electrode patternis formed by pulses of laser light from the laser.
 51. The method ofclaim 44 wherein the forming step includes removing at least 2% of theconductive material from the base.
 52. The method of claim 44 wherein atleast 5% of the conductive material is removed from the base.
 53. Themethod of claim 44 wherein at least 90% of the conductive material isremoved from the base.